Network: Multicast test using VLC

Overview

The purpose of this procedure is to check that your network is setup to correctly to handle multicast traffic. For further information and guidance on networking and multicast, please read our Successful Infinity Implementation guide.

This page will guide you through setting up an RTP multicast stream on VLC to generate multicast video traffic which will allow you to test the capability of your network for Infinity. You'll need at least three PCs, two with VLC installed for this test and a third to run a Wireshark to check that the mutlicast traffic is being handled correctly by an IGMP Querier and not being broadcast to all the network port.

The VLC version at the time of writing this guide was v3.0.8 Vetinariis.

Step 1

Getting Started

After starting VLC media player navigate to "Media" and the select "Stream..." from the drop down menu. This will start the configuration wizard for the streaming function within VLC.

Step 2

Choosing our data

Add a video file that you'll be streaming across the network. You can add as many video files here as you'd like and they will play as a playlist. I've redacted my file structure but it should still be clear for you. To add a video click "Add..." and select the files of your choice then click "Stream". You can then click "Next" on the next dialogue box, this is just to check that the source file structure is correct.

Step 3

Configuring the stream

Now we need to configure the type of stream we want. But first it's a good idea to tick the checkbox which says "Display locally". This will play the video on the streaming PC which gives us some confidence that the setup is working. From the drop down menu select "RTP / MPEG Transport Stream" and click "Add". Navigate to the "RTP/TS" tab and here we'll input the network configuration for our stream. We can use any multicast IP address and base port number that is available. In this example I'm using 239.255.0.1 and a base port of 5004. These are usually free on a network but consult the IT administrator first if this is likely to go onto the corporate network. The stream name is optional but I find it helpful to label it.

At the next dialogue box we want to untick "Activate Transcoding". This option would transcode our chosen files into a better format for streaming but we don't particularly mind in this test and it's CPU intensive. Then click "Next" to take us to the next dialogue.

This next step is optional. If you only have one network switch in your setup you can skip this step. Otherwise, by default, the stream will have a time to live of 1 which means it won't be routed past the first switch it's connected to. We can increase this by adding "ttl=10" into the { } section of the string. Once you've done this as shown below, you can click "Stream".

With this our stream is setup. And we should have the video playing on our computer.

Step 4

Receiving

With our stream setup, we need to next configure another device to receive it. To do this, open VLC on another computer and navigate to "Media" and this time select "Open Network Stream..." from the drop down menu.

The Open Media wizard will start which allows us to choose what network stream to request. Here we have to input the details on the stream we have configured and specify the type of stream. So here we input "rtp://239.255.0.1:5004" which is the <stream type>://<IP-address>:<base port>. Then click "Play" to open the stream. All things being well the video should start playing. It can sometimes take a minute to open the stream and it will be slightly delayed in comparison to the local video.

With that the stream is setup. You will now have multicast traffic on your network that you can use to test if your system is able to handle it.

Step 5

The third host will need to be connected to the same network switch but should run Wireshark instead to determine if the host is receiving unsolicited multicast traffic. In a fully provisioned network with IGMP configured correctly, only hosts who subscribe to the multicast traffic should receive it. When multicast traffic is not being handled correctly by an IGMP Querier, it becomes broadcast traffic, where every port on the network switch is sent the same traffic. This can cause the ports to become overwhelmed, typically resulting in packet loss. By using Wireshark to monitor the incoming traffic, it is possible to determine if multicast traffic is erroneously being received or not.

Please read the Using Wireshark to check if IGMP is configured guide.